I'm looking for a modern, streamlined and fully-featured email application to replace my ageing Seamonkey (previously known as Netscape/Mozilla) setup. I like its ability to have several different "User-profiles" meaning that I can neatly archive my old email and even have several different users on the same computer (without having to set up different Mac login-accounts). But Seamonkey is, in my honest opinion, getting a bit long in the tooth. Its user-interface is reminiscent of ancient Windows or Linux apps and I'd like to try out something more "Mac like", but with the same (or better) functionality. Which email apps out there can import and export the MBOX format (so that I can import my existing mail, and export mail when I need to archive, and use Seamonkey for viewing archived messages)?